TR4 nuclear receptor enhances prostate cancer initiation via altering the stem cell population and EMT signals in the PPARG-deleted prostate cells

Based on network pharmacology and molecular docking to predict the mechanism of Huangqi in the treatment of castration-resistant prostate cancer

Background

As a kind of traditional Chinese medicine, HQ is widely mentioned in the treatment of cancerous diseases in China, which has been proven to have a therapeutic effect on cancerous diseases, such as prostate cancer. To predict the specific mechanism of HQ in the treatment of CRPC, we will conduct preliminary verification and discussion based on a comprehensive consideration of network pharmacology and molecular docking.

Methods

TCMSP was used to obtain the compounds and reach the effective targets of HQ. The targets of CRPC were reached based on GeneCards database and CTD database. GO and KEGG were utilized for the analysis of overlapping targets. The software of Openbabel was used to convert the formats of ligands and reporters. In addition, molecular docking studies were performed by using the software of Autodock Vina.

Result

It can be seen from the database results that there were 87 active compounds (20 key active compounds) in HQ, and 33 targets were screened out for CRPC treatment. GO and KEGG pathway enrichment analyses identified 81 significant GO terms and 24 significant KEGG pathways. There is a difference in terms of the expression of core protein between cancer patients and healthy people. The expression of core protein in patients also has an impact on the life cycle. The results of molecular docking showed that the docking activity of drug molecules and core proteins was better.

Conclusions

It is concluded from the results of this network pharmacology and molecular docking that HQ makes a multi-target and multi-biological process, and results in the multi-channel synergistic effect on the treatment of CRPC by regulating cell apoptosis, proliferation and metastasis, which still needs further verification by experimental research.

The Epithelial-Mesenchymal Transition at the Crossroads between Metabolism and Tumor Progression

The transition between epithelial and mesenchymal phenotype is emerging as a key determinant of tumor cell invasion and metastasis. It is a plastic process in which epithelial cells first acquire the ability to invade the extracellular matrix and migrate into the bloodstream via transdifferentiation into mesenchymal cells, a phenomenon known as epithelial–mesenchymal transition (EMT), and then reacquire the epithelial phenotype, the reverse process called mesenchymal–epithelial transition (MET), to colonize a new organ. During all metastatic stages, metabolic changes, which give cancer cells the ability to adapt to increased energy demand and to withstand a hostile new environment, are also important determinants of successful cancer progression. In this review, we describe the complex interaction between EMT and metabolism during tumor progression. First, we outline the main connections between the two processes, with particular emphasis on the role of cancer stem cells and LncRNAs. Then, we focus on some specific cancers, such as breast, lung, and thyroid cancer.

Testicular Nuclear Receptor 4 Regulates Proliferation and Apoptosis of Bladder Cancer via Bcl-2

Testicular nuclear receptor 4 (TR4) is a member of the nuclear hormone receptor family and acts as a ligand-activated transcription factor and functions in many biological processes, such as development, cellular differentiation, and homeostasis. Recent studies have shown that TR4 plays an important role in prostate cancer, renal cell carcinoma, and hepatocellular carcinoma; however, its potential link to bladder cancer (BC) remains unknown. This study found that bladder cancer exhibited a higher expression of TR4 compared to normal tissues. Overexpressed TR4 promoted the bladder cancer cell proliferation, and knocked down TR4 with TR4-siRNA suppressed the bladder cancer cell proliferation. Mechanistic studies reveal that TR4 functions by altering the expression of Bcl-2 to regulate apoptosis in bladder cancer cells. Furthermore, knocking down Bcl-2 reversed the BC proliferation induced by TR4. In vivo, we also confirmed that TR4 knockdown mice (TR4^+/−) showed slower bladder cancer growth than wild-type mice (TR4^+/+) induced by the carcinogenic chemicals. Moreover, TR4^+/− mice showed a lower grade of histopathology than the control group. In conclusion, these results indicate that TR4 plays a key role in bladder cancer proliferation, and targeting TR4 would probably be a potential strategy for bladder cancer treatment.

Interplay between orphan nuclear receptors and androgen receptor-dependent or-independent growth signalings in prostate cancer

It is well-established that both the initial and advanced growth of prostate cancer depends critically on androgens and thus on the activated androgen receptor (AR) -mediated signaling pathway. The unique hormone-dependent feature of prostate cancer forms the biological basis of hormone or androgen-deprivation therapy (ADT) that aims to suppress the AR signaling by androgen depletion or AR antagonists. ADT still remains the mainstay treatment option for locally advanced or metastatic prostate cancer. However, most patients upon ADT will inevitably develop therapy-resistance and progress to relapse in the form of castration-resistant disease (castration-resistant prostate cancer or CRPC) or even a more aggressive androgen-independent subtype (therapy-related neuroendocrine prostate cancer or NEPC). Recent advances show that besides AR, some ligand-independent members of nuclear receptor superfamily-designated as orphan nuclear receptors (ONRs), as their endogenous physiological ligands are either absent or not yet identified to date, also play significant roles in the growth regulation of prostate cancer via multiple AR-dependent or -independent (AR-bypass) pathways or mechanisms. In this review, we summarize the recent progress in the newly elucidated roles of ONRs in prostate cancer, with a focus on their interplay in the AR-dependent pathways (intratumoral androgen biosynthesis and suppression of AR signaling) and AR-independent pathways or cellular processes (hypoxia, oncogene- or tumor suppressor-induced senescence, apoptosis and regulation of prostate cancer stem cells). These ONRs with their newly characterized roles not only can serve as novel biomarkers but also as potential therapeutic targets for management of advanced prostate cancer.

Metabolic Reprogramming and Epithelial-Mesenchymal Plasticity: Opportunities and Challenges for Cancer Therapy

Metabolic reprogramming and epithelial-mesenchymal plasticity are both hallmarks of the adaptation of cancer cells for tumor growth and progression. For metabolic changes, cancer cells alter metabolism by utilizing glucose, lipids, and amino acids to meet the requirement of rapid proliferation and to endure stressful environments. Dynamic changes between the epithelial and mesenchymal phenotypes through epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) are critical steps for cancer invasion and metastatic colonization. Compared to the extensively studied metabolic reprogramming in tumorigenesis, the metabolic changes in metastasis are relatively unclear. Here, we review metabolic reprogramming, epithelial-mesenchymal plasticity, and their mutual influences on tumor cells. We also review the developing treatments for targeting cancer metabolism and the impact of metabolic targeting on EMT. In summary, understanding the metabolic adaption and phenotypic plasticity will be mandatory for developing new strategies to target metastatic and refractory cancers that are intractable to current treatments.

Long non-coding RNA PRRT3-AS1 silencing inhibits prostate cancer cell proliferation and promotes apoptosis and autophagy

NEW FINDINGS

What is the central question of this study? What is the role of lncRNA PRRT3-AS1 in the regulation of peroxisome proliferator-activated receptor γ (PPARγ) gene-mediated mechanistic target of rapamycin (mTOR) signalling pathway in proliferation, apoptosis and autophagy of prostate cancer cells? What is the main finding and its importance? The targeting relation between lncRNA PRRT3-AS1 and PPARγ was verified, and it was demonstrated that silencing of lncRNA PRRT3-AS1 can upregulate apoptosis and autophagy yet downregulate proliferation, migration and invasion of prostate cancer cells through the mTOR signalling pathway. Further work is needed to consolidate the therapeutic value of lncRNA PRRT3-AS1 in clinical trials and treatment of prostate cancer.

ABSTRACT

Although long non-coding RNAs (lncRNAs) are correlated with multiple cancers, their molecular mechanisms in prostate cancer (PC) remain inadequately understood. This study investigated the effects of lncRNA PRRT3-AS1 on the progression of prostate cancer (PC) with involvement of peroxisome proliferator-activated receptor γ (PPARγ). Microarray analysis was used to identify the differentially expressed genes and lncRNAs associated with PC. RT-qPCR and western blot analysis were employed to test the expression of lncRNA PRRT3-AS1, mammalian target of rapamycin (mTOR) signalling pathway-, apoptosis- and autophagy-related genes. A scratch test, Transwell assay, CCK-8 assay, colony formation assay, flow cytometry and monodansylcadaverine staining were employed to identify the migration, invasion, proliferation activity, cell cycle and apoptosis and autophagy of PC3 cells, respectively. Tumorigenicity assays in nude mice were used to detect the tumorigenic ability. GSE55945 and GSE46602 datasets indicated that lncRNA PRRT3-AS1 was highly expressed in PC. PPARγ was predicted as a target gene of lncRNA PRRT3-AS1. Ectopic overexpression of PPARγ or lncRNA PRRT3-AS1 silencing led to inhibited cell viability, migration and invasion, and accelerated apoptosis. Furthermore, the delivery of si-PRRT3-AS1 or PPARγ vector to PC3 cells resulted in the regression of xenografts in nude mice. Based on the in vitro and in vivo experiments, silencing of lncRNA PRRT3-AS1 was observed to activate the PPARγ gene, which in turn could inhibit PC cell proliferation and promote apoptosis and autophagy by blocking the mTOR signalling pathway.

Macrophage inflammatory factors promote epithelial-mesenchymal transition in breast cancer

The majority of breast cancers (90-95%) arise due to mediators distinct from inherited genetic mutations. One major mediator of breast cancer involves chronic inflammation. M1 macrophages are an integral component of chronic inflammation and the breast cancer tumor microenvironment (TME). Previous studies have demonstrated that up to 50% of the breast tumor comprise of tumor-associated macrophages (TAMs) and increased TAM infiltration has been associated with poor patient prognosis. Furthermore, breast cancer associated deaths are predominantly attributed to invasive cancers and metastasis with epithelial-mesenchymal transition (EMT) being implicated. In this study, we investigated the effects of cellular crosstalk between TAMs and breast cancer using an in vitro model system. M1 polarized THP-1 macrophage conditioned media (CM) was generated and used to evaluate cellular and functional changes of breast cancer lines T47D and MCF-7. We observed that T47D and MCF-7 exhibited a partial EMT phenotype in the presence of activated THP-1 CM. Additionally, MCF-7 displayed a significant increase in migratory and invasive properties. We conclude that M1 secretory factors can promote a partial EMT of epithelial-like breast cancer cells. The targeting of M1 macrophages or their secretory components may inhibit EMT and limit the invasive potential of breast cancer.

TR2 and TR4 Orphan Nuclear Receptors: An Overview

Testicular nuclear receptors 2 and 4 (TR2, TR4), also known as NR2C1 and NR2C2, belong to the nuclear receptor superfamily and were first cloned in 1989 and 1994, respectively. Although classified as orphan receptors, several natural molecules, their metabolites, and synthetic compounds including polyunsaturated fatty acids (PUFAs), PUFA metabolites 13-hydroxyoctadecadienoic acid, 15-hydroxyeicosatetraenoic acid, and the antidiabetic drug thiazolidinediones can transactivate TR4. Importantly, many of these ligands/activators can also transactivate peroxisome proliferator-activated receptor gamma (PPARγ), also known as NR1C3 nuclear receptor. Both TR4 and PPARγ can bind to similar hormone response elements (HREs) located in the promoter of their common downstream target genes. However, these two nuclear receptors, even with shared ligands/activators and shared binding ability for similar HREs, have some distinct functions in many diseases they influence. In cancer, PPARγ inhibits thyroid, lung, colon, and prostate cancers but enhances bladder cancer. In contrast, TR4 inhibits liver and prostate cancer initiation but enhances pituitary corticotroph, liver, and prostate cancer progression. In type 2 diabetes, PPARγ increases insulin sensitivity but TR4 decreases insulin sensitivity. In cardiovascular disease, PPARγ inhibits atherosclerosis but TR4 enhances atherosclerosis through increasing foam cell formation. In bone physiology, PPARγ inhibits bone formation but TR4 increases bone formation. Together, the contrasting impact of TR4 and PPARγ on different diseases may raise a critical issue about drug used to target any one of these nuclear receptors.

Organ-specific gene modulation: Principles and applications in cancer research

Microarray and next generation sequencing has led to the exploration of correlated gene patterns and their shared functions. Gene modulators are proteins that alter the activity of transcription factors and influence the expression of their target genes. It is assumed that modulators are dependent on transcription factors. Several algorithms have been developed for the detection of gene modulators. On the other hand, it is becoming increasingly evident that modulators play a crucial role in carcinogenesis by interfering with fundamental biologic processes. Therapeutic gene modulation that is based on artificial modification of endogenous gene functions by designer molecules is an exciting new field of investigation.

Hepatocellular carcinoma: thyroid hormone promotes tumorigenicity through inducing cancer stem-like cell self-renewal

Cancer stem-like cells (CSCs) play a key role in maintaining the aggressiveness of hepatocellular carcinoma (HCC), but the cell-biological regulation of CSCs is unclear. In the study, we report that thyroid hormone (TH) promotes cell self-renewal in HCC cells. TH also increases the percentage of CD90 + HCC cells and promotes drug resistance of HCC cells. By analyzing primary human HCC samples, we found that TRα transcript level is significantly elevated in primary liver cancer and portal vein metastatic tumor, compared to that of adjacent normal liver tissue. Knocking down TRα not only inhibits HCC self-renewal in vitro but also suppresses HCC tumor growth in vivo. Interestingly, treatment of TH leads to activation of NF-κB, which is required for the function of TH on inducing HCC cell self-renewal. We also found TRα and p65 cooperatively drive the expression of BMI1 by co-binding to the promoter region of BMI1 gene. In summary, our study uncovers a novel function of TH signaling in regulating the CSCs of HCC, and these findings might be useful for developing novel therapies by targeting TH function in HCC cells.

TR4 Nuclear Receptor Different Roles in Prostate Cancer Progression

Nuclear receptors are important to maintain the tissue homeostasis. Each receptor is tightly controlled and under a very complicated balance. In this review, we summarize the current findings regarding the nuclear receptor TR4 and its role in prostate cancer (PCa) progression. In general, TR4 can inhibit the PCa carcinogenesis. However, when PPARγ is knocked out, activation of TR4 can have an opposite effect to promote the PCa carcinogenesis. Clinical data also indicates that higher TR4 expression is found in PCa tissues with high Gleason scores compared to those tissues with low Gleason scores. In vitro and in vivo studies show that TR4 can promote PCa progression. Mechanism dissection indicates that TR4 inhibits PCa carcinogenesis through regulating the tumor suppressor ATM to reduce DNA damages. On the other hand, in the absence of PPARγ, TR4 tends to increase the stem cell population and epithelial-mesenchymal transition (EMT) via regulating CCL2, Oct4, EZH2, and miRNA-373-3p expression that results in increased PCa carcinogenesis. In opposition to PCa initiation, TR4 can increase PCa metastasis via modulating the CCL2 signals. Finally, targeting TR4 enhances the chemotherapy and radiation therapy sensitivity in PCa. Together, these data suggest TR4 is a key player to control PCa progression, and targeting TR4 with small molecules may provide us a new and better therapy to suppress PCa progression.